Gravity. It's the law.

When planetary scientist Kelsi Singer studied images of Saturn’s icy moon Iapetus, she found something unexpected: huge ice avalanches. As far as moons go, Iapetus is as eccentric as they come. One half of the planet is light-colored and the other half is dark. It has 12-mile-high mountains — twice the height of Mount Everest. And a mountainous ridge bulges out at its equator, giving it the distinct appearance of a walnut.

The avalanches are “something we never expected to see on Iapetus,” said Singer, a graduate student in earth and planetary sciences at Washington University in St. Louis and lead author of a paper published today in Nature Geoscience.

These icy landslides are similar to long-runout landslides on Earth known as sturzstroms (German for fallstreams), which can travel a distance equal to 20 to 30 times the height they fall from. Normal landslides typically only travel twice the height they fall from.The Iapetus landslides were probably triggered by objects impacting the moon’s surface.

[continued at Wired Science]